I've been using M1 15w50 in my 03 harley since it was new. It has over 90,000 miles on it now, and the clutch has never been replaced, nor has it ever showed signs of slipping. I have adjusted it every 20,000 miles, and just replaced the original clutch cable last week. Not broken, just getting hard to pull, and lubrication didn't help. I have used M1 in all my harleys. I used Rotella for my first oil change on my Versys, and have no problems. I will probably use M1 15w50 in it from now on. I live in south Ms. and it is hot and humid here in the summer time.